Thread Coordination

Coordination Between Workers

• Problem:

  • Worker A is writing a document
  • Worker A needs an image that Worker B is producing
  • Worker A cannot continue until Worker B has finished

• One solution is to introduce a manager

  • The manager coordinates the two workers

Solution:

• Worker B tells the manager when they have finished

• The manager tells Worker A to resume work

  • B is working
  • A is waiting
  • B finishes their work
  • B tells manager
  • Manager tells A to resume
  • A resumes work

• Similar situations arise with threads

• E.g. A program which is performing a download

  • One thread fetches the data over the network
  • Another thread displays a progress bar
  • A third thread will process the data when the download is complete